You know, you’re starting to drift off into dreamland, but just as you’re about to slip headfirst into that deep sleep, you start to fall, or something hits you in the face, waking you from dreamworld in a sudden and startling manner.

You’ve ever been curious about this strange phenomena, even may be wondered why this happens. It’s something that happens to people on a regular basis.

Scientists have finally figured out what it means. They’ve even given it an official name, the “hypnic jerk.” The hypnic jerk is described differently by everyone, but commonly shared experiences say that it feels like falling. Oddly enough, its also been described as a demon choking you in your sleep.

Hypnic jerk is a brief and sudden involuntary contraction of the muscles of the body which occurs when a person is beginning to fall asleep, often causing the person to jump and awaken suddenly for a moment. Hypnic jerks are one form of involuntary muscle twitches called myoclonus.

Researchers think that a few external causes, like caffeine and tobacco, might increase how often the hypnic jerk happens to you. They recommend avoiding any caffeinated drinks if bedtime is only a few hours away. It’s also been seen that medications like Adderall and Ritalin can have similar effects, and sleep deprivation has been seen to trigger the phenomena as well.

The hypnic jerk is most often seen when a person falls asleep rapidly, during, or after they’ve been in an exhaustive state. On rare occasions, when the body is really exhausted the brain will process stages of sleep too quickly, confusing itself into thinking that the body and its major systems are failing.

It responds by jolting you awake with a burst of chemicals, one that the brain might interpret, and then build a dream designed to wake you up, which is the basic premise behind the theory of the ‘hypnic jerk.’